A085273 Difference between n-th composite number and its largest prime divisor.

2, 3, 6, 6, 5, 9, 7, 10, 14, 15, 15, 14, 11, 21, 20, 13, 24, 21, 25, 30, 22, 17, 28, 33, 19, 26, 35, 35, 33, 40, 23, 45, 42, 45, 34, 39, 51, 44, 49, 38, 29, 55, 31, 56, 62, 52, 55, 51, 46, 63, 69, 37, 70, 57, 66, 65, 75, 78, 41, 77, 68, 43, 58, 77, 85, 78, 69, 62, 47, 76, 93, 91

Offset

1,1

Links

Ivan Neretin, Table of n, a(n) for n = 1..10000

Example

For 91=7*13 we have 91-13 = 78.
For 92=2*2*23 we have 92-23 = 69.

Mathematica

DeleteCases[Table[n - FactorInteger[n][[-1, 1]], {n, 100}], 0 _] (* Ivan Neretin, Jun 20 2019 *)

Prog

(PARI) cminusp2(n) = { for(x=2, n, forstep(p=x, 2, -1, if(isprime(p) & x%p==0 & isprime(x)==0, print1(x-p, ", "); break); ) ) }

Crossrefs

Cf. A002808, A085271.

Sequence in context: A124498 A197334 A113399 * A151850 A290223 A274213

Adjacent sequences: A085270 A085271 A085272 * A085274 A085275 A085276

Keyword

easy,nonn

Author

Cino Hilliard, Aug 12 2003

Extensions

Offset corrected by Ivan Neretin, Jun 20 2019

Status

approved